Cirrhosis is a major cause of morbidity and mortality, and disease progression is associated with altered gut microbial composition and function. The only reliable cure for cirrhosis is liver transplant (LT). However, a sizable proportion of post-LT patients develop multi-drug resistant organisms (MDROs), cognitive impairment and metabolic syndrome, which can be life- threatening and result in long-term disability or incomplete recovery of pre-LT function. Moreover, using currently available biomarkers, it is unclear which patients will develop these post-LT adverse events and there is some evidence that altered gut microbiota plays an important role. This proposal represents the first step towards using pre-LT microbial modulation in preventing post-LT complications with the central hypothesis: Gut microbial composition and function before liver transplant can successfully predict post-transplant outcomes. We will study this hypothesis using the following specific aims: Aim 1: To determine the role of pre-transplant gut microbial composition and function in the prediction of post-transplant infections through MDRO colonization, Aim 2: To determine the role of pre-transplant gut microbial composition and function in the development of post-transplant metabolic syndrome, Aim 3: To determine the role of pre-transplant gut microbial composition and function in cognitive recovery after liver transplant The study will have 2 parts: Part 1 will utilize already collected longitudinal samples from 150 LT recipients from both centers. Part 2 will enroll 50 more patients per site to validate findings from part 1. Stool microbiota composition (16srRNA sequencing for diversity, relative abundance of potentially pathogenic and beneficial taxa, and specific molecular assays for MDRO colonization) and function (metabolomics, bile acids) will be performed. Cognitive function (validated paper-pencil and computerized techniques) and metabolic syndrome will be diagnosed post-LT. Pre-transplant microbial assessment will be used to predict these outcomes independent of already validated clinical predictors using bio-informatics. This will help guide future precision medicine based research on microbiota in prognosticating LT patients. The CTSAs at VCU and CUIMC are associated with leading LT centers with a long track record of clinical and translational research in cirrhosis, liver transplant, microbiota, and cognition. Both centers will collaborate equally in recruitment and analysis. This proposal fits with PAR-19-100 through the focus on Precision Medicine and Translational studies of the human microbiome.